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Full text of "Handbook Of Chemical Engineering - I"

POWER GENERATION AND TRANSMISSION                     5
RESIDUAL  VALUE,  PER LIFE, YEARS         CENT OF TOTAL
Buildings ...........................         10 to 40                1 to 5
Chimneys ..........................         10 to 40               0 to 10
Boilers .............................         15 to 25                2 to 20
Steam engines .......................         15 to 30                2 to 15
Steam turbines .......................         20 to 30                5 to 20
Electric generators ...................         20 to 30              10 to 25
Electrical auxiliaries ..................         20 to 25               10 to 20
Steam auxiliaries .....................         15 to 35                2 to 15
Gas producers ........ .' ..............         10 to 20                2 to 6
Gas engines ..........................         15 to 20                2 to 10
Oil engines ..........................         12 to 20                2 to 8
Waterwheels. . .......................         15 to 40                2 to 6
Gas auxiliaries — ....................           5 to 20                5 to 8
These figures are more conservative than those often quoted, and the residual values are higher. Experience indicates that used-up machinery ordinarily finds a market at second-hand prices considerably above those prevailing for junk material. Negative residual values are possible. The life of items like foundations is limited by that of the associated equipment. If A = amount to be realized to offset depreciation = initial cost— residual value, n = estimated life, r = rate of interest, S = annual depreciation charge, then
The blanket depreciation for the whole plant will usually be from 5 to 9 per cent of the initial cost.
Total Cost. — In steam plants, the labor cost per kilowatt-hour is usually between 0.1 and 1.0 ct., being high for small plants and low-load factors. Miscellaneous items (water, lubricants, supplies, repairs, maintenance and supervision) range from 0.05 to 0.20 ct.," varying chiefly with size. These items may amount to from 3 to 12 per cent of the total operating cost. The fuel cost will usually be from one-half to two-thirds of such total operating cost. Fixed charges vary from one-half to four -fifths the operating cost, the higher ratios arising with the lower load factors.
Gas power plants involve a slightly higher labor cost, and a miscellaneous expense much higher. Fixed charges are higher than for steam because the initial investment is higher. Oil engines and waterwheels involve less labor and incidental expense than any of the other forms of power.
Purchased Power. — Rates are usually based on the purchaser's load factor: often by combining a fixed charge based on " readiness to serve" and a rate per kilowatt-hour actually consumed. Thus if the customer's peak load is 1,000 kw. and his annual load factor is 0.40, a rate of $15 per year per kilowatt for service and 2 cts. per kilowatt-hour for consumption would lead to an annual charge of $15,000 + (8,760 X 0.40 X 1,000 X $0.02) = $85,080, or the actual cost per kilowatt-hour would be 2.43 cts. If the plant should be shut down for a month, the rate would automatically increase.
Heating. — To warm average factory buildings requires about 2 B.t-.u. per cubic foot per hour in the coldest weather, or about half this during average